The present invention relates to a cleaning method for use in an electrophotographic copying machine, and more particularly to a cleaning method for removing toner images remaining on a photoconductor by use of a cleaning blade.
Conventionally, as a cleaning method in general use for an electrophotographic copying machine, a fur brush cleaning method is known. In this method, since toner particles removed from the photoconductor by a fur brush are collected in a filter bag by a vacuum suction apparatus, this method has shortcomings, such as the cleaning apparatus becoming oversized, and the vacuum suction apparatus making loud noises, and it being difficult to reuse the toner recovered in the filter bag. Furthermore, there are known a magnetic brush cleaning method and a roller cleaning method. In the case of the magnetic brush cleaning method, the cleaning effect is inferior to the other cleaning methods. Accordingly, the magnetic brush cleaning method is not useful, except in a special process. To be more specific, in the case of the magnetic brush cleaning method, as the toner concentration in the magnetic brush increases during continuous cleaning, the cleaning effect is gradually reduced. Accordingly, some special apparatus for removing only the toner from said magnetic brush is necessary. On the other hand, in the case of the roller cleaning method, it has a cleaning effect similar to that of the blade cleaning method. However, the main cleaning effect of the roller cleaning method is attained by trapping toner in the numerous pores in the surface of the roller. Therefore, when the pores have been filled with toner, the cleaning effect is extremely reduced. In order to prevent this, a scraper is brought into pressure contact with the surface of the roller to remove toner from the pores and to reuse the roller for cleaning. However, since the scraper is in pressure contact with the surface of the roller, the surface of the roller is abraded so that the diameter of the roller is changed significantly or the useful life of the roller is shortened or a complicated pressure application mechanism is required.
The present invention relates to a blade cleaning method with a high cleaning efficiency. Conventionally, in this sort of the blade cleaning method, a cleaning blade is normally in pressure contact with the surface of a photoconductor. However, such a system is inconvenient for replacing a photoconductor drum, and furthermore, since unnecessary pressure is applied to the surface of the photoconductor drum, it becomes a problem that the surface of the photoconductor drum is changed physically or chemically while in use. Therefore, in a more recent apparatus, the cleaning blade is brought into contact with and moved away from the surface of the photoconductor drum or the surface of a photoconductor belt in synchronism with a drive motor for driving the photoconductor drum or belt. Alternatively, the pressure of the cleaning blade is released when an image formation portion passes over a cleaning station after copying.
However, the system of synchronizing the contacting and separating movement of the cleaning blade with the actuation of the drive motor has the following shortcomings: Even if the cleaning blade is moved away from the surface of the photoconductor drum by releasing the pressure of the cleaning blade as soon as the drive motor is stopped, the photoconductor drum is moved slightly by its inertia after the drive motor has been stopped. Since there always exist toner particles in the contact portion between the end portion of the cleaning blade and the photoconductor drum, when the cleaning blade is moved away from the photoconductor drum 1, the photoconductor drum 1, with part or all of the toner particles thereon, passes over the cleaning station as shown in FIG. 1. Furthermore, the portion of the photoconductor drum 1 moved by ther inertia thereof is uncleaned, which is indicated by N1 in FIG. 1. Accordingly, the next copying cannot be started immediately. This is because when a latent electrostatic image is formed on the photoconductor drum 1 with toner remaining thereon, the obtained copy quality is poor. Likewise, when a print button is depressed, the photoconductor drum 1 is moved before the cleaning blade 2 is brought into pressure contact with the photoconductor drum 1, because it takes time to bring the cleaning blade 2 into contact with the photoconductor drum 1 since the cleaning blade 2 is positioned away from the drum 1.
Therefore, as shown in FIG. 2, there is formed an additional uncleaned portion N2. Images cannot be formed in these uncleaned portions N1 and N2.
Furthermore, in the case where the photoconductor drum 1 is driven with a lump of toner particles T thereon as shown in FIG. 1 and the lump of toner particles T comes to a position where it can be dropped under its own weight, the lump of toner particles is separated from the photoconductor drum 1 and is scattered in the copying machine, smearing the inside of the copying machine and bringing about significant lowering of the performance of the copying process. In a cleaning blade system capable of moving the cleaning blade away from the photoconductor drum 1 after the latter image formation portion N2 has passed through the cleaning station, the above-mentioned disadvantages still occur.